Nummy is a cooler way of saying awkward. You can also express the feeling of awkwardness with "nums" for short. No, nummy does not mean "tasty," as you might think. It is nummy that people think that...

"That kid thinks nummy means yummy"
"Nummy, breh!

"Wow, didn't those two just break up, but now they're best friends?"
"Totally nums breh!"